“We didn’t find anything else from the east coast – just these very distinctive grains,” says Barham. “Initially, we thought there might be some volcanism in Western Australia, but we couldn’t find any evidence.”

Two clues ruled out the possibility that river systems had carried the zircon crystals across the country: they were so well preserved and fossils in the rocks indicated that the crystals were of an identical age.

Staggering power

The finding points to the sheer force of the east coast volcanoes, says Barham. The eruptions would have been tens to hundreds of times more powerful than any documented in human history. An equivalent eruption today would be heard in the west coast city of Perth.

Tremendous volcanic activity was happening all around the world 100 millions of years ago due to the disintegration of the supercontinent Gondwana, says Scott Bryan at Queensland University of Technology in Brisbane.

Modern volcanoes can spew fine particles of ash that are carried by winds over large distances, as happened in 2010 when Iceland’s Eyjafjallajökull volcano released an ash plume that grounded flights across Europe.

But they lack the power to hurl larger particles thousands of kilometres.